Q) Velocity of 4 gas molecules are respectively 4m/s, 6m/s, 7m/s and 9m/s. What will be their rms velocity?
(a) $\sqrt{45.5} ms^{-1}$
(b) $52m^2s^{-2}$
(c) $45.5ms^{-1}$
(d) $45.5m^2s^{-2}$
My attempt:
$$\sqrt{\frac{4^2+6^2+7^2+9^2}{4}}$$
$$=\sqrt{45.5} ms^{-1}$$
So, (a) should be the answer. However, the answer sheet says that the answer is (d).
Aren't they wrong?